Fincher’s Zodiac is a masterpiece, a truly great movie that is setting 2007 off on as strong a footing as any film in memory. Part of the movie’s greatness comes from two amazing performances – Robert Downey Jr’s portrayal of San Francisco Chronicle reporter Paul Avery and Mark Ruffalo as detective Dave Toschi.

Toschi is a larger than life character – he was part of the basis for Steve McQueen’s Bullitt, down to the unique holster he always wore. And in the first Dirty Harry, Toschi’s famous Zodiac case was reborn as the Scorpio case – and solved in a way that Toschi could not.

I had a chance to talk to Ruffalo at a roundtable here in New York City today. He was candid and unassuming, really coming across like the kind of actor who cares more about acting than being famous.

Zodiac opens this Friday. You must see it.

Ruffalo: One interviewer today said to me, ‘How does it feel that your first job, You Can Count On Me’ is still your best work?’ I agreed with him. [laughs]

Q: You’ve played a couple of police officers. How do you make this one different?

Ruffalo: 90% of it was being with Dave Toschi. Another 5%, maybe more, was the investigative work I was doing to be a cop, to know about the case. The character I think you would define by the choices he makes in a moment of stress. Dave Toschi, his character, I think is pretty strong. But the character is Dave Toschi, that [gets into his Toschi voice from the film] quiet way of talking, that sincere, measured way of talking… that’s Dave Toschi. The idiosyncratic things, the animal crackers, the way he dressed, all of that is original Dave Toschi.. DT!

Q: Dave had been the basis for Bullitt, and he saw his case taken and made into Dirty Harry. When you came to him, was he like, ‘You Hollywood bastards!’ or was he pretty friendly?

Ruffalo: He was a little reticent. His wife didn’t want him to have anything to do with this movie. [The case] cost them an enormous amount as a family, and Dave who he was as a person, and his career. When I showed up our conversation started something like, [Toschi voice] ‘Umm, thank you for coming… Why do you want to talk to me? You’re the big Hollywood movie star.’ I was like, oh shit, here we go. He wasn’t mean about it, but there was a certain amount of distrust. I said to him, ‘I’m here to honor you. I’m here to get it right. I know this is a big part of your life and I wouldn’t dare to try and portray you without being able to hear it from your mouth.’ I could never have come up with the Dave Toschi I had in this movie without him. Never in a million years could I have gotten the kind of idiosyncratic behavior that that guy has.

Q: Some of your strongest scenes in the movie are with Jake Gyllenhaal. What’s he like to work with?

Ruffalo: He was good. I’ve known Jake for a long time, and it was good to work with him. It was fun to see him really kind of stretch his wings with somebody like Dave Fincher. They were tough scenes, and they took a lot of building, but I’m happy the way they ended up. It’s a good performance, and I think it’s one of his best. As much as he talks about being put through the wringers, it paid off for him.

Q: Was that your experience with Fincher as well? Jake talked to the New York Times about how difficult the process was for him, and Fincher is known for being very exacting. Was your experience similar to his?

Ruffalo: I can only respect an artist like Fincher. I can only respect somebody who puts that kind of demands on himself and the people around him. I can only respect a man who doesn’t think good enough is good enough. So I didn’t see it the way some people saw it – to me that’s ‘Waah waah waah.’ I mean, to me, we get paid a lot of money and there are people who work a lot frickin’ harder – most everyone on the set. If you had to do a few extra takes… To hear that makes me cringe. Please god, don’t think we’re all like this.

Q: Did you find yourself getting more and more fascinated with the case as you researched it for the film?

Ruffalo: I’m not a big Zodiac [guy]. I didn’t know it well, I’m not a true crime guy. But working on it, as I started to enter the world of Dave Toschi and the investigation, I did become a little obsessed with it. There was constant conjecture on who did it, and this piece of information… people were coming in all the time with their own theories. You sit around with a group of actors, the last thing you have to worry about is people talking and sharing their ideas. There was a constant debate going on that made it really interesting. That drew us in.

Q: Do you think it’s Arthur Lee Allen?

Ruffalo: He’s the best suspect there ever was, but I take the side of Dave Toschi, which is there’s a due process of law, and where’s the beef. That one piece of evidence that really sticks it to that guy never materialized. This movie is as much about due process of law as it is about anything. You see in the world where we are today when due process of law is thrown out and we go by gut feelings and trumped up evidence. The one thing these guys can be accused of is following the letter of the law too closely. There’s so much to the movie beyond your character. What was your thought when you finally saw the whole thing?

Ruffalo: Wow. I saw a rough cut in Dave Fincher’s office – it didn’t have any music, it wasn’t sweetened – and I was really blown away. What I saw, what Fincher was actually going for, is so different from anything else he’s ever made. I thought this is something to be really proud of. I didn’t know how the rest of the world would react to it, and usually my tastes run counter to the popular culture, so I didn’t know how it would be seen, but I just thought, ‘Damn, this is a daring piece of film work by a major director for a major studio.’ Who’s doing that, really?

What’s amazing is that you know they don’t catch the guy in the end, but you go along for the journey anyway!

Q: This movie is almost like journalism in how it delivers facts and information. For many actors having to give that kind of exposition is a nightmare – how did you keep from crossing the line of making all that information boring?

Ruffalo: There’s that stuff, and then there’s the desire to catch the guy, which keeps the scene interesting. Then there’s what’s going on inside them personally – some people are falling apart, some people are eating themselves up. It’s everything that’s under the words, how richly you can build that life under the words. The simple things like the procedural and the jargon, what’s built under the surface of those is what makes it work.

Q: As an actor how do you approach that?

Ruffalo: It’s all character work. Your desire has to be so great – what it costs you, what it’s costing that character – if that’s working inside you and your motor is going as an actor, the audience sees that and they’re interested. It happens in a way they’re not quite aware of, and what it is is that they’re seeing themselves in the movie in a weird way.

Q: You’re often seen a serious actor, but you do very light movies like 13 Going on 30 or Just Like Heaven in between these very serious parts.

Ruffalo: I come from the theater, where you can do whatever the hell you want; they expect it from you. You’re not stuck as a romantic or comedic or tragedian… you can do what you want. I always thought the best way of acting is one foot in the grave and one on the banana peel. I feel that the best drama has some humor in it and the best humor has some humor in it.

I did a bunch of dark movies, and my nieces could never see anything I had done. I was like, it would be fun to do a romantic comedy. I really admire Marcello Mastroianni, he had such a great career. He was dramatic and he was funny – he did everything. I was like, you know what, I’m just going to do whatever I feel like doing. I’m not going to follow any mold and I’m not going to do what anybody tells me. I’m going to do a movie my nieces can watch – and also a movie I think has a really positive message for young girls. That movie says something, and I’m into that game. I like movies that say something. Even Just Like Heaven is saying something about life, about the way you live your life and love – the power of love. Some of the stuff might seem flip, but to me it has an important meaning. It’s another way to reach people and give part of the human experience to them.

Q: Speaking of messages, does this film say something about our lives post-9/11, with the boogeyman out there and this formless fear people experience?

Ruffalo: It doesn’t surprise me that this movie is happening at this moment and that it’s getting the attention of people and people are relating to it. It might not be so up front as that – this is film theory, this is deep stuff – but as an artist I like to think that is true. You see it all over the culture, we’re dealing with dark material right now and paranoia. It’s everywhere – even this year’s fashions are dark and heavy and gothic and medieval. There’s something in the subconscious.

Q: Your next film is going to be with the excellent Rian Johnson on The Brothers Bloom. Can you talk about your character and what you’ll be doing?

Ruffalo: Stephen Bloom. I play the older brother of the Brothers Bloom con man couple. They’ve been confidence men since they were young boys. The younger brother, who’s been the sort of the flawed romantic hero of all these elaborate cons is sick of it. He wants to live an unwritten life, so we set up this huge con where, in the end, he’ll be able to walk away from being a con man and find true love. It’s out there, man. It’s very literary. It starts with magical realism and gets heavy at the end. There’s a lot of embedded symbolism, but it’s a great con man movie, too. A lot of it’s based on The Sting. It’s a cross between The Sting and The Last Waltz. [laughs]

Q: Was it the script that drew you in or had you seen Brick?

Ruffalo: I got the script and he starts it in rhyming quartets. I was like, what am I reading? It’s out there. I have to say it’s out there, but this kid has raised 30 million dollars to make a con man movie with real panache and style, and I have to say I think that guy has enormous panache and style and is one of our really interesting filmmakers, so I’m up for that game. Plus it’s a part I’ve never done – it’s a lot of language, the character is very flamboyant. It’s going to be shot in Eastern Europe and have a lot of anachronistic qualities. It’s going to be fun, and I’m excited.